Heat pipe structure with an external liquid detouring path

ABSTRACT

A heat pipe structure with an external liquid detouring path includes a main pipe having an interior space and divided into a top portion, a middle portion and a bottom portion. In the middle portion, a circular liquid-collecting groove facing the top portion is constructed for collecting a liquid drained down along the inner wall of the pipe. The heat pipe also includes a bifurcated pipe to detour the liquid in the liquid-collecting groove to the bottom portion of the heat pipe.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to an improved heat pipe structure, and moreparticularly to a heat pipe having a bifurcated path to bypass acondensed liquid back to a lower portion of the heat pipe.

(2) Description of the Prior Art

Application of a heat pipe apparatus is to utilize physical phase changeof a work fluid sealed in the heat pipe to perform heat transportationbetween two ends of the heat pipe, respectively located in twoenvironments with a thermal difference. Referring to FIG. 1, a schematiccross-sectional view of a conventional heat pipe 1 in a typicaloperational state is shown. The heat pipe 1, usually made of ahigh-thermal-conductivity material such as a copper, is mainly anairtight pipe structure 10. The internal space of the airtight pipestructure 10 contains a specific amount of work fluid 11 for performingphysical phase change.

In the art, the heat pipe 1 is firstly to have one end open forinjecting the work fluid 11 and for vacuuming the internal space of thepipe 1. Then, the end is sealed to form an airtight state of the heatpipe 1.

In application of the heat pipe 1, it is posed vertically as shown inFIG. 1 or at an high-elevation angle in the two work areas 200, 300. Theambient temperature of the upper work area 200 is lower than that of thelower work area 300. The operational boiling point of the work fluid 11is between the ambient temperatures of the upper and the lower workareas, 200 and 300 respectively.

In the art, the portion of the heat pipe 1 located in the lower workarea 300 is called a vaporization portion 12, while the portion thereoflocated in the upper area 200 is called a condensation portion 13. Inoperations, the work fluid 11 sitting inside the vaporization portion 12of the heat pipe 1 can absorb the heat in the lower work area 300 so tobe vaporized as a steam floating into the condensation portion 13 in theupper work area 200. Through walls of the pipe 10, the steam of the workfluid 11 can be cooled down to condensate as liquid drops by the upperwork area 200. By gravity forcing, the liquid drops of the work fluid 11can drop directly back into or slip along the walls down into thevaporization portion 12. Upon such an arrangement, a rapid heattransportation pathway can be established to begin in the lower workarea 300, via the reciprocally movement and phase change of the workfluid 11 inside the heat pipe 1, and end up finally in the upper workarea 200.

In the aforesaid application of the heat pipe 1, the heat transferbetween the lower work area 300 and the upper work area 200 isautomatically in action as soon as the heat pipe 1 is anchored inbetween. No more external forcing or switching is required. Yet, in aparticular case that the rate of heat-absorbing in the vaporizationportion 12 (i.e. heat flow from the lower work area 300 to the heat pipe1) is elevated to an over-heat situation, all the work fluid 11 in thevaporization portion 12 may be transformed into the steam state and nomore work fluid 11 in the liquid state can stay at the bottom of theheat pipe 1. Such a dry bottom phenomenon in the heat pipe 1 is called adual reverse flow state of the heat pipe structure.

While the heat pipe 1 meets a dual reverse flow state, the liquid dropsof the work fluid 11 condensed at the condensation portion 13 would bevaporized before reaching the bottom of the vaporization portion 12.Though the phase change operation of the work fluid 11 inside the heatpipe 1 can still prevail, yet the lower portion of the vaporizationportion 12 can loose its ability in absorbing the surrounding heat. Inparticular, in the case that the lower portion of the vaporizationportion 12 is utilized to remove a heat from a specific heat-generatingdevice, it is quite possible that the device will quickly fail or beeven damaged.

Referring now to FIG. 2, a conventional loop-type heat piping is shown.In the piping as shown, the vaporization portion 12 and the condensationportion 13 are separated at a predetermined distance, but are bridged bya vapor pipe 14 and a liquid pipe 15. In application, the vaporizationportion 12 can be directly mounted onto a heat-generating device. Thesteam of work fluid generated inside the vaporization portion 12 is sentautomatically to the far-end condensation portion 13 via the vapor pipe14. In the condensation portion 13, the steam is then cooled down by thesurroundings to condense and form a liquid state of the work fluidthereinside. The liquid state of the work fluid is driven automaticallyback to the vaporization portion 12 via the liquid pipe 15.

In the application of the loop-type heat piping as shown in FIG. 2, forthe vapor pipe 14 and the liquid pipe 15 are separate, the liquid canarrive the vaporization portion 12 without being heated in a mid-way.

Therefore, the dual reverse flow state of the work fluid as mentionedabove can never occur in this type of heat piping. As a result, theheat-generating device can be better protected by the loop-type heatpiping.

Nevertheless, though the loop-type heat piping may simply provide asolution to the single-tube heat pipe as shown in FIG. 1, yet thecomplicated structuring, the required construction space and the cost ofthe loop-type heat piping are still there to be further considered.Definitely, a complete substitution of the single-tube heat pipe by theloop-type heat piping is hardly to be possible. Therefore, an effort toimprove the single-tube heat pipe for avoiding the notorious dualreverse flow phenomenon is surely welcome to the skilled in the art.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a heatpipe structure with an external liquid detouring path, in which abifurcated pipe is constructed exteriorly to the main pipe structure forbypassing a condensed liquid back to a lower portion of the heat pipe,so that the dual reverse flow phenomenon for heat piping can beprevented and thus a normal operation of the heat pipe can bemaintained.

The heat pipe structure in accordance with the present inventioncomprises a slender hollow main pipe having an interior spaceaccommodating a work fluid. Further, the interior space can be dividedinto a top portion, a middle portion and a bottom portion. The topportion and the bottom portion are respectively located in acondensation portion and a vaporization portion as described in aconventional heat pipe, while the middle portion is located at theconjunction area of the condensation portion and the vaporizationportion. The middle portion of the present invention has a circularliquid-collecting groove facing the top portion for collecting the workfluid in a liquid state drained down along an inner wall of the heatpipe. Further, an external bifurcated pipe is included to bridgespatially the liquid-collecting groove and the bottom portion fordetouring the work fluid in the liquid-collecting groove to the bottomportion.

In one embodiment of the present invention, the liquid-collecting grooveof the heat pipe can be formed by an inner wall and an outer rim of aliquid-collecting ring plugged inside the middle portion. Theliquid-collecting ring further includes a through hole in communicationspatially with both the top portion and the bottom portion.

In one embodiment of the present invention, the main pipe of the heatpipe can be formed by telescoping or joining an upper half pipe and alower half pipe, in which the lower half pipe further includes a top endbent radial inward and upward to plug into the upper half pipe so as toform the liquid-collecting groove in between with the inner wall of theupper half pipe.

In one embodiment of the present invention, the main pipe of the heatpipe can be formed by telescoping or joining an upper half pipe and alower half pipe, in which the upper half pipe further includes a bottomend bent radial inward and upward to form thereof the liquid-collectinggroove.

In one embodiment of the present invention, the main pipe of the heatpipe can be formed by joining an upper half pipe, a liquid-collectingring and a lower half pipe, in which an upper portion of theliquid-collecting ring is located inside the upper half pipe so as toform thereof the liquid-collecting groove in between with the upper halfpipe.

In one embodiment of the present invention, the bottom portion of theinterior space of the heat pipe can have a bottom end thereof enlargedto form a fluid room, and respectively a bottom (wall) of the main pipecorresponding to the fluid room is also extended to form aheat-collecting part to be mounted on a heat-generating device. In theembodiment, a lower end of the bifurcated pipe can be connected to a topside or a lateral side of the heat-collecting part of the bottomportion.

In one embodiment of the present invention, the inner wall of the mainpipe located above the liquid-collecting groove can be laminated with acapillary layer for rapidly transporting liquid drops of the work fluiddownward from the top portion of the heat pipe into theliquid-collecting groove.

All these objects are achieved by the heat pipe structure with anexternal liquid detouring path described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be specified with reference to itspreferred embodiment illustrated in the drawings, in which:

FIG. 1 is a schematic cross-sectional view of a conventional single-tubeheat pipe in operations;

FIG. 2 is a schematic view of a conventional loop-type heat piping;

FIG. 3 is a perspective view of a first embodiment of the heat pipestructure with an external liquid detouring path in accordance with thepresent invention;

FIG. 4 is a cross-sectional view of FIG. 3 along line a-a in operations;

FIG. 5 is a cross-sectional view of a second embodiment of the heat pipein accordance with the present invention;

FIG. 6 is a cross-sectional view of a third embodiment of the heat pipein accordance with the present invention;

FIG. 7 is a cross-sectional view of a fourth embodiment of the heat pipein accordance with the present invention;

FIG. 8 is a perspective view of a fifth embodiment of the heat pipe inaccordance with the present invention;

FIG. 9 is a cross-sectional view of FIG. 8 along line b-b;

FIG. 10 is a perspective view of a sixth embodiment of the heat pipe inaccordance with the present invention;

FIG. 11 is a cross-sectional view of FIG. 8 in operations; and

FIG. 12 is an enlarged cross-sectional view of a portion of the mainpipe of the heat pipe in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention disclosed herein is directed to a heat pipe structure withan external liquid detouring path. In the following description,numerous details are set forth in order to provide a thoroughunderstanding of the present invention. It will be appreciated by oneskilled in the art that variations of these specific details arepossible while still achieving the results of the present invention. Inother instance, well-known components are not described in detail inorder not to unnecessarily obscure the present invention.

To simplify the description of the present invention, elements servingthe same purpose but having slight difference in appearance will benamed and labeled uniquely.

In the present invention, the condensed liquid drained down along theinner wall of the heat pipe is the major concern. For a convention heatpipe as shown in FIG. 1 to meet a dual reverse flow phenomenon, thosecondensed liquid would be vaporized in the midway of the heat pipe andthus never reach the bottom end of heat pipe. As a consequence, thebottom end of the heat pipe would be dried out and loose its function inabsorbing the external heat. Contrarily, it is the design logic of thepresent invention that the down flow of the condensed liquid isinterrupted at midway of the heat pipe, led out of the main pipe toprevent from being vaporized before reaching the bottom end of the heatpipe, and finally sent back directly into the bottom end for performinganother cycle of phase change operation. Upon such an idea, the bottomend of the heat pipe can be never dried up and can always be refilledwith fluid in liquid state. Thus, the serving purpose of the heat pipecan be better fulfilled.

Referring now to FIG. 3 and FIG. 4, a first embodiment of the heat pipestructure in accordance with the present invention is respectively shownin a perspective view and a cross-sectional view along line a-a of FIG.3. In the embodiment, the heat pipe 2 comprises a slender hollow mainpipe 20 that has a sealed interior space 204 further accommodating asubstantial amount of work fluid 11. As shown, the interior space 204can be divided into a top portion 203, a middle portion 202 and a bottomportion 201. The top portion 203 and part of the middle portion 202 areresembled to the condensation portion 13 of FIG. 1, and the bottomportion 201 and another part of the middle portion 202 are resembled tothe vaporization portion 12 of FIG. 1.

As shown, the inner wall 207 of the main pipe 20 at the middle portion202 is structured to form a circular liquid-collecting groove 221 facingthe top portion 203 for collecting the work fluid 11 in a liquid state(i.e. the condensed liquid) drained down along the inner wall 207thereabove. Further, the heat pipe 2 of the present invention furtherincludes an external bifurcated pipe 21. The bifurcated pipe 21 has anupper end 211 and an opposing lower end 212, in which the upper end 211is connected with the liquid-collecting groove 221 for leading the workfluid 11 out of the main pipe 20, and in which the lower end 212 isconnected with the bottom portion 201 for refilling the work fluid 11back to the main pipe 20, more specifically to the bottom of the heatpipe 2. Upon such an arrangement, the condensed work fluid 11 can detourvia the bifurcated pipe 21 to bypass the hi-temperature area in thebottom portion 201 and the middle portion 202 of the main pipe 20 sothat no dual reverse flow phenomenon and the dry-up bottom can be foundin the heat pipe structuring 2 of the present invention.

In the first embodiment, the liquid-collecting groove 221 of the heatpipe 2 is formed by plugging a liquid-collecting ring 22 into the mainpipe 20 at the middle portion 202. As shown in FIG. 4, the circularconcave space formed between the outer rim 222 of the liquid-collectingring 22 and the an inner wall 207 at the middle portion 202 can thus beused as the liquid-collecting groove 221 of the present invention. Theconical liquid-collecting ring 22 further includes a through hole 220for bridging spatially the top portion 203 and the bottom portion 201.By providing the liquid-collecting ring 22, the steam of the work fluid11 can freely rise from the bottom portion 201 to the top portion 203via the through hol3 220, and the liquid work fluid 11 drained downalong the inner wall 207 above the middle portion 202 can besuccessfully collected in the liquid-collecting groove 221.

In the present invention, the connection between the bifurcated pipe 21and the main pipe 20 can be made by firstly drilling the main pipe 20 atproper locations and then welding or threading the ends 211, 212 of thebifurcated pipe 21 to the respective drilled holes on the main pipe 20.Or, third connecting parts can also be introduced to engage the ends211, 212 of the bifurcated pipe 21 with the main pipe 20. However,possible connection means for engaging the bifurcated pipe 21 and themain pipe 20 are well known to the skilled person in the art, so relateddetails regarding such connections will be omitted herein.

In the present invention, the bifurcated pipe 21 can be made of copper,appropriate metal, or plastics. While a plastic pipe is used as thebifurcated pipe 21, two connecting parts are required to engage theplastic bifurcated pipe 21 to the metal main pipe 20.

Referring now to FIG. 5, a second embodiment of the heat pipe structurein accordance with the present invention is shown in a cross sectionalview. Compared to the first embodiment of FIG. 4, the main pipe 20 ofthis embodiment is formed by telescoping or joining an upper half pipe20 a and a lower half pipe 20 b. The upper half pipe 20 a has its topend sealed, while the lower half pipe 20 b has its bottom end sealed. Asshown, the lower half pipe 20 b further includes a top end bent radialinward and upward to form a taper head for plugging into the upper halfpipe 20 a. By providing the taper head of the lower half pipe 20 b, theliquid-collecting groove 22 can be formed between the inner wall 207 ofthe upper half pipe 20 a and the taper head (i.e. the liquid-collectingring 22 in this embodiment).

In the second embodiment, the introduction of the bifurcated pipe 22 isthe same as that in the first embodiment.

Referring now to FIG. 6, a third embodiment of the heat pipe structurein accordance with the present invention is shown in a cross sectionalview. Compared to the first embodiment of FIG. 4 and the secondembodiment of FIG. 5, the main pipe 20 of the heat pipe 2 in this thirdembodiment is formed by joining an upper half pipe 20 a, aliquid-collecting ring 22 having a central through hole 220, and a lowerhalf pipe 20 b. An upper portion 222 of the liquid-collecting ring 22 islocated inside the upper half pipe 20 a such that the liquid-collectinggroove 221 can be formed by the limited circular space between the upperportion 222 and the upper half pipe 20 a. Also, the inclusion of thebifurcated pipe 22 in this third embodiment is the same as that in thefirst embodiment or in the second embodiment.

In the third embodiment of the present invention, the connection betweenthe liquid-collecting ring 22 and the upper half pipe 20 a or thatbetween the liquid-collecting ring 22 and the lower half pipe 20 b canbe a welding connection, a pure press-tight connection, or a threadingconnection. In the case that a threading connection is adopted, anexternal thread can be made to the liquid-collecting ring 22 and acorresponding internal thread can be made to the upper half pipe 20 a orthe lower half pipe 20 b. Also, while in engaging threads of theliquid-collecting ring 22 and the upper half pipe 20 a or the lower halfpipe 20 b, appropriate seal parts such as O-rings or air-tight belts canbe applied in between. Yet, such a piping connection technique is wellknown to the skilled person in the art, and details will be omittedherein.

Referring now to FIG. 7, a fourth embodiment of the heat pipe structurein accordance with the present invention is shown in a cross sectionalview. Compared to the first embodiment of FIG. 4 and the secondembodiment of FIG. 5, the main pipe 20 of this embodiment is also formedby telescoping or joining an upper half pipe 20 a and a lower half pipe20 b. The upper half pipe 20 a has its top end sealed, while the lowerhalf pipe 20 b has its bottom end sealed. As shown, a bottom end 22 ofthe upper half pipe 20 a is bent radial inward and upward so as todirectly form thereof the liquid-collecting groove 22. Also, theconstruction of the bifurcated pipe 22 in this fourth embodiment is thesame as that in any of previous embodiments.

Referring now to FIG. 8 and FIG. 9, a fifth embodiment of the heat pipestructure in accordance with the present invention is shown in aperspective view and a cross sectional view of FIG. 8 along line b-b,respectively. In this embodiment, the inner wall 207 at the bottomportion 201 of the interior space 204 of the heat pipe 2 is enlarged toform a heat-collecting part 23 having a fluid room 233. Theheat-collecting part 23 is used to mount on a heat-generating device(not shown in the figure). As shown in the embodiment, the lower end 212of the bifurcated pipe 21 is connected to a top side 230 of theheat-collecting part 23. That is to say that the liquid work fluid 11collected in the liquid-collecting groove 221 is led directly to thefluid room 233 of the bottom portion 201 via the bifurcated pipe 21.

In the fifth embodiment of the present invention, the construction ofthe main pipe 20 is similar to that of the second embodiment as shown inFIG. 5. Yet, a major difference in between is that the upper half pipe20 a of the fifth embodiment is extended to sleeve tightly over thelower half pipe 20 b till the lower end of the upper half pipe 20 a hitsthe top side 230 of the heat-collecting part 23.

Referring now to FIG. 10, a sixth embodiment of the heat pipe structurein accordance with the present invention is shown in a perspective view.Compared to the fifth embodiment of FIG. 8, the sixth embodiment has thelower end 212 of the bifurcated pipe 21 connected to a lateral side 231of the heat-collecting part 23 of the main pipe 20.

Referring now to FIG. 11, a cross-sectional view of FIG. 8 in operationsis shown. As shown, the heat-collecting part 23 of the heat pipe 2 isdirectly mounted on a heat-generating device 4. The heat generated inthe heat-generating device 4 is led into the fluid room 233 to boil thework fluid 11 thereinside. The steam of the work fluid 11 then floatsupward freely in the interior space 204 of the main pipe 20 from thefluid room 233 of the bottom portion 201 to the top portion 203. In thetop portion 203, the steam exchanges heat with the inner wall 207thereof so as to condense to form liquid drops of the work fluid 11.Part of the liquid drops fall directly down through the interior space204 to the fluid room 233, while part of the liquid drops formed on theinner wall 207 at the top portion 203 of the main pipe 20 would draindown along the inner wall 207 to be collected by the liquid-collectinggroove 221 at the middle portion 202. The work fluid 11 collected by theliquid-collecting groove 221 is then detoured out of the main pipe 20 bythe bifurcated pipe 21 and thereafter refilled into the fluid room 233of the heat-collecting part 23. In the fluid room 233, the work fluid 11is again to begin another cycle of phase change operation as describedabove.

As shown, to speed up the heat dissipation from the main pipe 20 to thesurroundings, an appropriate fin structure 3 is constructed at thecondensation portion of the heat pipe 2 (including the top portion 203and an upper part of the middle portion 202). Preferably, a fan (notshown in the figure) can be used to enhance the dissipation efficiencyof the fin structure 3.

In the present invention, the heat-collecting part 23 can be shaped as ahollow disk body, a hollow square body, a hollow thin plate body, or anytype of hollow body that can fit a particular shape of theheat-generating device 4.

Referring now to FIG. 12, an enlarged cross-sectional view of a portionof the main pipe of the heat pipe in accordance with the presentinvention is shown. As shown, the inner wall 207 of the main pipe 20located above the liquid-collecting groove 221 is laminated with acapillary layer 208 for rapidly transporting liquid drops of the workfluid at the inner wall 207 of the heat pipe downward into theliquid-collecting groove 221. Such a capillary layer and itsconstruction are well known to the skilled person in the art, and sodetails will be omitted herein.

In the present invention, by providing an external liquid detouring path(i.e. the bifurcated pipe) to the single-tube heat pipe structure, thecondensed work fluid can then bypass the vaporization portion of theheat pipe and can be sent directly to the lower portion of the heatpipe. Upon such an arrangement, the dual reverse flow phenomenon forheat piping can be avoided in the heat pipe of the present invention anda normal operation of the heat pipe can be ensured.

While the present invention has been particularly shown and describedwith reference to a preferred embodiment, it will be understood by thoseskilled in the art that various changes in form and detail may bewithout departing from the spirit and scope of the present invention.

1. A heat pipe structure, comprising a main pipe having an interiorspace accommodating a work fluid, the interior space being divided intothereof a top portion, a middle portion and a bottom portion,characterized in that: the middle portion has a circularliquid-collecting groove facing the top portion for collecting the workfluid in a liquid state drained down along an inner wall of the heatpipe, and a bifurcated pipe is included to bridge the liquid-collectinggroove and the bottom portion for detouring the work fluid in theliquid-collecting groove to the bottom portion.
 2. The heat pipestructure according to claim 1, wherein said liquid-collecting groove isformed by said inner wall and an outer rim of a liquid-collecting ringplugged inside said middle portion, and the liquid-collecting ringfurther includes a through hole in communication spatially with bothsaid top portion and said bottom portion.
 3. The heat pipe structureaccording to claim 1, wherein said main pipe is formed by joining anupper half pipe and a lower half pipe, in which the lower half pipefurther includes a top end bent radial inward and upward to plug intothe upper half pipe so as to form said liquid-collecting groove withsaid inner wall at the upper half pipe.
 4. The heat pipe structureaccording to claim 1, wherein said main pipe is formed by joining anupper half pipe and a lower half pipe, in which the upper half pipefurther includes a bottom end bent radial inward and upward to formthereof said liquid-collecting groove.
 5. The heat pipe structureaccording to claim 1, wherein said main pipe is formed by joining anupper half pipe, a liquid-collecting ring and a lower half pipe, inwhich an upper portion of the liquid-collecting ring is located insidethe upper half pipe so as to form said liquid-collecting groove inbetween with the upper half pipe.
 6. The heat pipe structure accordingto claim 1, wherein said bottom portion has a bottom end thereofenlarged to form a fluid room while a bottom of said main pipecorresponding to the fluid room is also extended to form aheat-collecting part to be mounted on a heat-generating device, whereina lower end of said bifurcated pipe is connected to a top side of theheat-collecting part.
 7. The heat pipe structure according to claim 1,wherein said bottom portion has a bottom end thereof enlarged to form afluid room while a bottom of said main pipe corresponding to the fluidroom is also extended to form a heat-collecting part to be mounted on aheat-generating device, wherein a lower end of said bifurcated pipe isconnected to a lateral side of the heat-collecting part.
 8. The heatpipe structure according to claim 1, wherein said inner wall of saidmain pipe located above said liquid-collecting groove is laminated witha capillary layer.
 9. A heat pipe structure, comprising: an upper halfpipe, formed as a pipe having an upper end sealed; a lower half pipe,formed as a pipe having a lower end sealed; a liquid-collecting ring,formed as a conical ring having a central through hole, located betweenthe upper half pipe and the lower half pipe, further having an upperportion thereof located inside the upper half pipe so as to have acavity between the upper portion and the upper half pipe formed as aliquid-collecting groove; and a bifurcated pipe, further having an upperend and an opposing lower end, the upper end connecting with theliquid-collecting groove, the lower end connecting with a bottom of thelower half pipe close to the lower end.
 10. The heat pipe structureaccording to claim 9, wherein said liquid-collecting ring and the lowerhalf pipe is made as a unique piece.
 11. The heat pipe structureaccording to claim 9, wherein said liquid-collecting ring and the upperhalf pipe is made as a unique piece.
 12. The heat pipe structureaccording to claim 9, wherein said bottom of said lower half pipe isenlarged to form a heat-collecting part to be mounted on aheat-generating device.
 13. The heat pipe structure according to claim9, wherein said upper half pipe is laminated thereinside with acapillary layer.